1. Field of the Invention
This invention relates to treadmills with trampoline-like surfaces and, more particularly, to an improved suspension system for connecting the movable mat or belt between supporting rails adjacent to the edges of the belt in such an apparatus.
Treadmills utilize an endless moving belt that allows an individual to walk, jog or run in place. Treadmills are useful not only for exercise, but for rehabilitation programs and medical testing such as the "stress test" which is commonly used. There is a demand for treadmills in indoor health clubs since many clubs are not able to build a running track and a treadmill provides the capability of a well-rounded exercise program.
Most treadmills are formed with a thin, endless belt that travels over a supporting surface so that the belt can withstand the weight of the individual using it. The rigid surface beneath the belt in these treadmills can cause shin splints or other stress-related injuries to the legs of the user. The use of treadmills of this design in rehabilitation programs is limited because of the impact on the legs of the users.
It has been found that a treadmill which utilizes a trampoline-like surface with a built-in resiliency reduces impact on the legs of the users to the point where such a machine can be used as a primary therapeutic aid for rehabilitation from leg injuries, because it significantly reduces the wear and tear on the legs of the user.
2. Description of the Related Art
U.S. Pat. No. 4,938,473 which issued on Jul. 3, 1990, describes such a treadmill with a trampoline-like surface. The suspension system of this treadmill is formed of transporter assemblies that included one or more springs spaced at an angle between each spring carrier and the belt to provide lateral support and stability for the belt. However, belts which utilize springs have a tendency to be unstable and the spring fatigue caused the belt to become slack, requiring periodic adjustment.
Further, springs proved to increase the expense of fabrication and maintenance to the machine due to spring failure and spring cuts.
An improvement over the treadmill with a trampoline-like surface described in U.S. Pat. No. 4,938,473, is described in U.S. Pat. No. 5,250,012, in which the springs located between the belt and rails were eliminated. The improvement included the use of a belt with built-in spring-like properties that was resilient along its width, but resisted stretching lengthwise.
A further improvement over the treadmills described above is described in U.S. Pat. No. 5,330,401 in which a suspension system utilizing a flexible wire cable as part of the transporter assembly for supporting the belt between the support rails was devised. This cable system reduced costs and at the same time allowed the proper tensioning in the belt to be achieved quickly and easily. However, the transporter assemblies used for connecting the flexible cables to the support rails were formed of a relatively large number of moving parts and restricted the high-end speed of the running surface, as well as making the fabrication difficult and expensive.
Therefore, there is a need for providing a transporter assembly for connecting the belt to the supporting rails formed of a simple design which would maximize the speed of the running surface and reduce fabrication time and expense.